Standalone Window Size Not Displaying In Fullscreen

Setting the standalone window size does not seem to have any effect, and using the -fullscreen parameter does not display the window in fullscreen.

Setting the Standalone Window Size to 1920x1080 and adding the -fullscreen command opened up a fullscreen window as expected in 4.11.2 binary. As a result, this is a regression.

Found in 4.12.2 binary. Reproduced in Main CL 3014400

1. Open the editor
2. Go to Edit->Editor Preferences->Play
3. Set the Standalone Window Size to 1920x1080
4. Click the dropdown arrow under the Play in Standalone Game category
5. In the Additional Launch Parameters section, use the -fullscreen command
6. Play in Standalone

Result: Standalone window displays at original size

Expected: Window would open in 1920x1080 fullscreen.